The project goal is to determine whether influenza vaccine (trivalent inactivated vaccine or TIV) can reduce childhood pneumonia burden including: influenza-associated, other aetiology-mediated, and overall pneumonia incidence. The specific objectives are to determine influenza vaccine efficacy on 1) early childhood pneumonia (children < 2 years), 2) laboratory-confirmed influenza and 3) the rates of influenza-specific complications including severe disease, hospitalisation, and otitis media. Secondary objectives include determining the effect of influenza vaccine on household transmission and associated complications among all age groups, the effect on proven non-influenza viral and bacterial invasive diseases, the occurrence of adverse events associated with the vaccine, and to measure immune responsiveness to influenza vaccine in these young children.